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Analog Devices Inc. LT3478EFE-1#TRPBF
- Part No.:
- LT3478EFE-1#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3478EFE-1#TRPBF.pdf
- Description:
- IC LED DRV RGLTR PWM 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,596
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Product details
Overview
LT3478EFE-1#TRPBF from Analog Devices (formerly Linear Technology) is a 4.5A monolithic boost LED driver IC with integrated 60mΩ/42V NPN switch, designed for constant-current driving of high-brightness LED strings in automotive and industrial lighting. It supports true-color PWM dimming up to 3000:1, operates from 2.8V to 36V input, delivers up to 1050mA LED current, and features programmable soft-start, open-LED protection, and thermal derating via dual CTRL pins.
For engineers reviewing the LT3478EFE-1#TRPBF datasheet, LT3478EFE-1#TRPBF pinout, LT3478EFE-1#TRPBF application, or LT3478EFE-1#TRPBF equivalent, key selection criteria include its 16-pin TSSOP package with exposed pad, integrated current-sense resistor (LT3478-1 variant), 200kHz–2.25MHz programmable switching frequency, and dual-temperature-compensated LED current control architecture.
Technical Context
The LT3478EFE-1#TRPBF implements a current-mode boost converter topology where LED current-not output voltage-serves as the primary feedback signal. Its transconductance error amplifier (VC pin) regulates peak switch current to maintain precise constant-current output across varying LED forward voltages and input conditions.
True Color PWM™ dimming is achieved by synchronizing external MOSFET gate drive with internal oscillator timing while preserving VC loop stability; the CTRL1/CTRL2 dual-input architecture enables independent programming of maximum LED current and temperature-dependent current derating without external op-amps or thermistors.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.8V to 36V - supports wide automotive battery range including cold-crank (6V) and load-dump (36V) transients |
| Max LED Current | 1050mA - full-scale output with ±5% accuracy over temperature, enabled by internal 0.1Ω sense resistor |
| Switch Rating | 4.5A, 42V, 60mΩ - handles peak inductor currents up to 6.8A and sustains continuous 4.5A conduction |
| Dimming Range | 3000:1 PWM - maintains consistent LED chromaticity across entire dimming range via synchronized gate control |
| Switching Frequency | 200kHz to 2.25MHz - set by RT-to-ground resistor; higher frequencies reduce inductor size but increase switching losses |
| Operating Temp | –40°C to 125°C junction - qualified for under-hood automotive applications with thermal shutdown and derating |
| OVP Threshold | Programmable 12.3V to 41V - via OVPSET pin (OVP = OVPSET × 41V), protects against open-LED fault conditions |
Pinout & Package
LT3478EFE-1#TRPBF is housed in a 16-lead thermally enhanced TSSOP package with exposed pad (Pin 17), requiring soldering to PCB ground plane for thermal management (θJA = 35°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (1,2) | Switch collector node | Fused internal NPN power switch output; connects to inductor and Schottky diode anode; minimize trace area for EMI reduction |
| VIN (3) | Main input supply | Primary power source for bias and switch base drive; requires local 10µF ceramic bypass to PGND |
| VS (4) | Inductor supply rail | Separate input for inductor bias; can be shorted to VIN if single supply used; enables optimized inrush control |
| L (5) | Inductor sensing node | Internal resistor between VS and L monitors inductor current; triggers immediate shutdown at >6A peak |
| VOUT (6) | Boost output voltage | Regulated output node; monitored internally for open-LED OVP detection; connect 4.7–10µF low-ESR ceramic capacitor |
| LED (7) | LED string return | Current-sense reference point; internal 0.1Ω resistor (LT3478-1) connects VOUT–LED for accurate 100–1050mA programming |
| OVPSET (8) | OVP threshold programming | Sets VOUT overvoltage limit (OVP = OVPSET × 41V); 0.3V–1V input yields 12.3–41V protection window |
| VC (9) | Error amplifier output | Transconductance amplifier output controlling switch peak current; used for loop compensation and soft-start discharge |
| VREF (10) | 1.24V bandgap reference | Stable 1.24V reference (±2.2%) supplying ≤100µA; used to bias CTRL1/CTRL2/OVPSET resistor dividers |
| SHDN (11) | Enable/UVLO control | 1.4V threshold with 10µA hysteresis; programs system UVLO using resistor divider; 0V reduces quiescent current to 3µA |
| CTRL1 (12) | Max LED current setpoint | Voltage input (0.1–1.05V) directly programs LED current: ILED = Min(CTRL1, 1.05)V × 1A/V |
| CTRL2 (13) | Temp-based current derating | Accepts negative-tempco voltage to reduce LED current above breakpoint; prevents thermal runaway and extends LED life |
| PWM (14) | PWM dimming enable | 1V threshold; drives external NMOS in LED cathode path; supports 100Hz–10kHz PWM signals up to 15V |
| RT (15) | Frequency programming | Resistor-to-ground sets fSW: 9.09kΩ = 2.25MHz, 31.6kΩ = 1.12MHz, 200kΩ = 200kHz |
| SS (16) | Soft-start timing | Capacitor-to-ground sets startup ramp time; discharges during fault to latch shutdown until capacitor recharges below 0.25V |
| PGND (17) | Power ground / thermal pad | Exposed copper pad; must be soldered to solid PCB ground plane for thermal dissipation and noise immunity |
Key Features
| Feature | Design Value |
|---|---|
| Integrated LED current sense | 0.1Ω internal resistor eliminates external RSENSE, reducing BOM count and layout sensitivity vs. LT3478 |
| True Color PWM™ dimming | Maintains constant LED color across 3000:1 dimming range by preserving forward voltage and junction temperature stability |
| Dual CTRL pin architecture | CTRL1 sets max current; CTRL2 independently programs temperature-dependent derating curve-no external thermistor or op-amp needed |
| Inrush current protection | Internal monitoring of L pin current disables switch at >6A peak, preventing inductor saturation and input rail collapse |
| Programmable open-LED protection | OVPSET pin allows user-defined overvoltage threshold (12.3–41V) to detect open-circuit LED string faults and halt switching |
Applications
| Automotive TFT LCD Backlight | High-Brightness Headlamp Auxiliary |
|---|---|
Use Scenario: Driving 6× white Luxeon III LEDs (15W total) from 8–16V automotive battery in instrument cluster backlight. IC Role / Device Role / Timing Role: Constant-current boost controller regulating 700mA per string with 500kHz switching and True Color PWM dimming for ambient light adaptation. Use Value: Eliminates need for ballast resistors and factory calibration; achieves uniform brightness and stable white point across 0–100% dimming. | Use Scenario: Powering auxiliary daytime running lights (DRL) using 4× high-flux LEDs in series, operating continuously at elevated under-hood temperatures. IC Role / Device Role / Timing Role: High-reliability LED driver with automatic thermal derating-CTRL2 programmed to reduce current above 85°C to prevent LED degradation. Use Value: Extends LED lifetime by 3× versus fixed-current drivers; maintains safe junction temperature without external thermal sensors. |
| Commercial Aircraft Cabin Lighting | Industrial Machine Vision Illumination |
Use Scenario: Controlling multi-zone LED arrays in passenger cabin lighting systems requiring DALI-compatible dimming and EMI compliance. IC Role / Device Role / Timing Role: Primary DC/DC stage converting 28V aircraft bus to regulated LED current; PWM input synchronized to DALI gateway signal. Use Value: Meets DO-160 Section 20 EMI limits via programmable 2.25MHz switching; 3000:1 dimming enables smooth fade transitions. | Use Scenario: Driving high-intensity red/blue LED arrays for barcode scanners and optical inspection systems requiring strobed illumination with microsecond timing precision. IC Role / Device Role / Timing Role: Fast-response current source enabling <10µs PWM edge transitions; SS pin controlled externally for repeatable startup timing. Use Value: Enables sub-millisecond strobe pulses with zero current overshoot; eliminates image blur in high-speed camera capture. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-power LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3478EFE#TRPBF | Uses external RSENSE; supports >1A current and higher accuracy at low currents (10mV/RSENSE) | Preferred when design requires >1050mA or sub-100mA precision; needs extra resistor and layout care | Select LT3478EFE#TRPBF only if external sense resistor is required for extended current range or improved low-current accuracy. |
| LT3965EFE#TRPBF | 4-channel independent buck LED driver; 50mA–5A per channel; I2C interface; no integrated switch | Used in multi-string RGBW systems requiring per-channel digital dimming and diagnostics | Choose LT3965EFE#TRPBF for multi-string, digitally addressable architectures-not for single-string high-power boost applications like LT3478EFE-1#TRPBF. |
Compared with LT3478EFE#TRPBF, the LT3478EFE-1#TRPBF reduces component count via integrated sense resistor but trades off flexibility in current range and low-current accuracy; versus LT3965EFE#TRPBF, it offers simpler analog control and higher single-channel power density but lacks digital configurability and multi-string support.
Availability
LT3478EFE-1#TRPBF is available at Aetrix Electronics and suitable for automotive lighting, industrial machine vision, commercial aircraft cabin systems, and high-reliability LED backlighting requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT3478EFE-1#TRPBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving automotive, industrial, communications, and aerospace markets.
The LT3478/LT3478-1 product line was engineered specifically for high-efficiency, thermally robust LED driving in harsh environments-emphasizing true-color dimming fidelity, integrated protection, and simplified thermal design for under-hood and avionics applications.
FAQ
What is the maximum LED current supported by the LT3478EFE-1#TRPBF?
The LT3478EFE-1#TRPBF supports a maximum LED current of 1050mA, with typical accuracy of ±5% over temperature. This is achieved using its internal 0.1Ω current-sense resistor and CTRL1 pin voltage programming (ILED = Min(CTRL1, 1.05)V × 1A/V). At 700mA output, the device maintains ±3.5% regulation across –40°C to 125°C junction temperature.
How does the LT3478EFE-1#TRPBF achieve True Color PWM dimming?
The LT3478EFE-1#TRPBF achieves True Color PWM dimming by maintaining constant LED junction temperature and forward voltage during dimming cycles. Its internal architecture synchronizes PWM gate drive with the VC error amplifier loop, preventing current transients that cause chromatic shift. This enables stable white-point retention across the full 3000:1 dimming range at frequencies from 100Hz to 10kHz.
Can the LT3478EFE-1#TRPBF operate from a 12V automotive battery with load-dump transients?
Yes, the LT3478EFE-1#TRPBF supports input voltages from 2.8V to 36V and is rated for automotive load-dump conditions. Its absolute maximum VIN rating is 36V, and internal circuitry clamps transient energy via the VS and L pins. For sustained 36V operation, thermal design must ensure junction temperature remains ≤125°C using the exposed pad and adequate copper area.
What is the purpose of the CTRL2 pin on the LT3478EFE-1#TRPBF?
On the LT3478EFE-1#TRPBF, the CTRL2 pin enables programmable LED current derating versus temperature. When biased with a negative temperature coefficient voltage (e.g., via NTC/resistor divider from VREF), CTRL2 overrides CTRL1 above a user-defined temperature breakpoint-reducing LED current to prevent thermal runaway and extend lifetime. This eliminates need for external thermal sensors or microcontroller intervention.
Does the LT3478EFE-1#TRPBF require external components for open-LED protection?
No, the LT3478EFE-1#TRPBF provides fully integrated open-LED protection. The OVPSET pin allows direct programming of the overvoltage threshold (12.3V–41V) using a single resistor to ground. When VOUT exceeds this threshold-indicating an open LED string-the IC immediately halts switching, discharges the SS pin, and latches shutdown until fault clearance and soft-start reset.
LT3478EFE-1#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Step-Down (Buck), Step-Up (Boost)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 2.8V
- Voltage - Supply (Max):
- 36V
- Voltage - Output:
- 42V
- Current - Output / Channel:
- 4.5A (Switch)
- Frequency:
- 200kHz ~ 2.25MHz
- Dimming:
- PWM
- Applications:
- Backlight
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP-EP
LT3478EFE-1#TRPBF FAQ
1.How can I place an order for LT3478EFE-1#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3478EFE-1#TRPBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LT3478EFE-1#TRPBF reliable?
The price and inventory of LT3478EFE-1#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3478EFE-1#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3478EFE-1#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3478EFE-1#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3478EFE-1#TRPBF?
LT3478EFE-1#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3478EFE-1#TRPBF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LT3478EFE-1#TRPBF?
For technical support, including LT3478EFE-1#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3478EFE-1#TRPBF requirements.
6.How does Aetrix verify that LT3478EFE-1#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3478EFE-1#TRPBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LT3478EFE-1#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3478EFE-1#TRPBF?
All LT3478EFE-1#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3478EFE-1#TRPBF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LT3478EFE-1#TRPBF part is unused and in its original packaging.
Return procedure for LT3478EFE-1#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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